DMD optimization bug?
Dmitry Olshansky
dmitry.olsh at gmail.com
Fri Mar 22 01:14:10 PDT 2013
22-Mar-2013 11:26, Jacob Carlborg пишет:
> On 2013-03-21 22:46, Iain Buclaw wrote:
>> On 21 March 2013 20:29, Jacob Carlborg <doob at me.com
>> <mailto:doob at me.com>> wrote:
>>
>> The code below works fine without optimizations. But with
>> optimizations (the -O flag) turned on it segfaults. The behavior
>> with optimizations turned on is a bit different depending on which
>> version of DMD I try and if I compile for 32 or 64bit.
>>
>> DMD 2.062 64bit: Segfault
>> DMD 2.062 32bit: Prints a huge array then segfault
>> DMD 2.061 64bit: Segfault
>> DMD 2.061 32bit: Prints a fairly small array (10 elements) with
>> random numbers
>> DMD head (7dcc72a997) 32bit: Bus error: 10
>>
>> I'm using Mac OS X 10.8.2.
>>
>> import std.stdio;
>>
>> int[]* getDeserializedSlice ()
>> {
>> void[] a = [1, 2, 3, 4, 5].dup;
>> auto b = &a;
>>
>> if (auto c = b)
>> auto d = &(cast(int[]) *c)[1 .. 1 + 2];
>>
>> return null;
>> }
>>
>> void main ()
>> {
>> writeln(*getDeserializedSlice(__));
>> }
>>
>> Is the above code supposed to work? The test case might look a bit
>> strange, the full source code is here:
>>
>>
>> https://github.com/jacob-__carlborg/orange/blob/master/__orange/serialization/__Serializer.d#L1672
>>
>>
>> <https://github.com/jacob-carlborg/orange/blob/master/orange/serialization/Serializer.d#L1672>
>>
>>
>> --
>> /Jacob Carlborg
>
> Crap, that example was incorrect, it should look like this:
>
> return &(cast(int[]) *c)[1 .. 1 + 2];
OK so c points to [1, 2, 3, 4, 5] (and who knows if it's 5 bytes or 5
ints) slice. *c is that slice, (cast(int[])*c)[1..3] is pieces of that
slice an r-value.
Mmm so you are returning a pointer to r-value (a local temporary)?
What's the point of the code?
--
Dmitry Olshansky
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